A gunman has shot dead a top member of the Afghan peace council in Kabul, striking another blow to efforts to negotiate a political resolution to the decade-long war.

Arsala Rahmani, a former Taliban official turned Afghan peace negotiator, was in his vehicle when he was killed by an unknown attacker at an intersection in the west part of the city, according to Mohammad Zahir, head of the Kabul police department's criminal investigation division.

Rahmani, a former member of parliament, was one of about 70 influential Afghans and former Taliban appointed by President Hamid Karzai to try to reconcile with the insurgents.

On Twitter, the US Embassy in Kabul called the assassination of another peace council member "a tragedy."